“Water is one of the most fundamental molecules on Earth, and yet scientists are only just beginning to wrap their heads around how bizarre the substance really is.”
https://www.sciencealert.com/physicists-just-showed-water-can-exist-as-two-different-liquids
Interesting to read that water can also be in a plasma like state.
readed that, very interesting
stan101 said:
“Water is one of the most fundamental molecules on Earth, and yet scientists are only just beginning to wrap their heads around how bizarre the substance really is.”https://www.sciencealert.com/physicists-just-showed-water-can-exist-as-two-different-liquids
Interesting to read that water can also be in a plasma like state.
Read that. Um … as a fluid dynamicist I’m familiar with some of the more unusual properties of water, but this has caught me completely unexpectedly. I would like to say that it’s either rubbish or a major breakthrough, but I can’t. Not without delving more deeply into the experimental methods.
By “plasma-like-state” they just mean supercritical. Supercritical water is present on Uranus and Neptune, for example, it exists at high pressure over a wide range of temperatures, and at higher temperatures is heavily ionised into H+ and OH-.
But the rest of the article is about water at room temperature and pressure, and about ice at room pressure.
I have no idea what these claimed 70 unique properties may me.
What lends credence to what this article is saying is that the boomerang-like shape of the water molecule would, in the absence of charge separation, pack very tightly but because of the charge dipole really doesn’t know how to pack together, which is why water has such a low melting point and also explains why normal ice is less dense than water, as well as the existence of amorphous ice.
http://www.pnas.org/content/early/2017/06/23/1705303114.abstract
Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar.
… slow and fast forms on the nanometre scale … low and high viscosity.
mollwollfumble said:
why water has such a low melting point and also explains why normal ice is less dense than water, as well as the existence of amorphous ice.
Moll, I just had a quick look regarding amorphous ice and it seems rapid cooling is the cause. The Wiki page states “Amorphous ice is produced either by rapid cooling of liquid water (so the molecules do not have enough time to form a crystal lattice or by compressing ordinary ice at low temperatures.)
Although almost all water ice on Earth is the familiar crystalline ice Ih, amorphous ice dominates in the depths of interstellar medium, making this likely the most common structure for H2O in the universe at large.”
So for the ice to crystalise rapidly, it must have been liquid water at some stage whilst in space and therefore space was warm enough for long enough and the rapidly cooled to create the amorphous ice. Would that take place when water is created as a byproduct from stars? Or am I wildly confused here?
“It has been postulated that water’s hydrogen-bonding network can exist in two liquid forms of different density, namely high- and low-density liquid water (HDL and LDL, respectively). These forms were recently simulated as metastable free-energy basins and a liquid–liquid transition was observed in the ST2 molecular model of water. Furthermore, it is hypothesized that the observed high- and low-density amorphous ice forms (HDA and LDA, respectively) are the glassy counterparts of the two liquid forms found deeply in the metastable supercooled regime.”
“To address the questions concerning the nature of the glass transition and hypothesized polymorphism of water, we use experimental X-ray techniques that probe the structure and dynamics of amorphous ice, as HDA transitions to the low-density form at ambient pressure. The diffraction pattern was recorded both in wide- and small-angle X-ray scattering (WAXS and SAXS, respectively) geometry. Using X-ray diffraction at WAXS geometry, one can distinguish between the high- and low-density forms. Changes in the speckle pattern reflect the dynamics at the nanometer length scale.”
A double peak occurs at a temperature of 130 Kelvin. Is this two forms of ice or liquid? It appears to be two kinds of melting, or perhaps a transition from HDL to LDL? There is only one form at temperatures of 110 K and below.
“The diffusivity obtained here is the strongest indication of liquid-like motion between 115 and 130 K and evidence for HDL and LDL. During the HDL-to-LDL transition at 130 K, the diffusion coefficients slow down by nearly an order of magnitude.”
So, not two types of water at room temperature.
mollwollfumble said:
“It has been postulated that water’s hydrogen-bonding network can exist in two liquid forms of different density, namely high- and low-density liquid water (HDL and LDL, respectively). These forms were recently simulated as metastable free-energy basins and a liquid–liquid transition was observed in the ST2 molecular model of water. Furthermore, it is hypothesized that the observed high- and low-density amorphous ice forms (HDA and LDA, respectively) are the glassy counterparts of the two liquid forms found deeply in the metastable supercooled regime.”“To address the questions concerning the nature of the glass transition and hypothesized polymorphism of water, we use experimental X-ray techniques that probe the structure and dynamics of amorphous ice, as HDA transitions to the low-density form at ambient pressure. The diffraction pattern was recorded both in wide- and small-angle X-ray scattering (WAXS and SAXS, respectively) geometry. Using X-ray diffraction at WAXS geometry, one can distinguish between the high- and low-density forms. Changes in the speckle pattern reflect the dynamics at the nanometer length scale.”
A double peak occurs at a temperature of 130 Kelvin. Is this two forms of ice or liquid? It appears to be two kinds of melting, or perhaps a transition from HDL to LDL? There is only one form at temperatures of 110 K and below.
“The diffusivity obtained here is the strongest indication of liquid-like motion between 115 and 130 K and evidence for HDL and LDL. During the HDL-to-LDL transition at 130 K, the diffusion coefficients slow down by nearly an order of magnitude.”
So, not two types of water at room temperature.
I wonder if life could exist in the above, it is liquid water just very different to our liquid water
> So for the ice to crystalise rapidly, it must have been liquid water at some stage whilst in space and therefore space was warm enough for long enough and the rapidly cooled to create the amorphous ice. Would that take place when water is created as a byproduct from stars? Or am I wildly confused here?
My reading is that in space, the pressure is so low that water would sublime straight from gas to solid, without passing through a liquid phase. This occurs at all pressures below 0.5% of Earth’s atmosphere, below 500 Pa. Compare that with 0.1 to 0.6 Pa in the Sun’s corona. The stars create a little oxygen and have lots of hydrogen. Far enough away from the star that the temperature and UV light doesn’t ionise the hydrogen, all the free oxygen will combine with the pervasive hydrogen to form water vapour.
The condensation as solid would occur as this low pressure gas encounters a cold dust grain.
Cymek said:
I wonder if life could exist in the above, it is liquid water just very different to our liquid water
Hmm, not a bad question. The water has ultra-high viscosity, which would slow down growth enormously. But on the other hand the complete lack of ice crystals would stop the problem of ice crystals puncturing cell walls.
Thanks.
stan101 said:
Thanks.
I didn’t quite answer your question.
I actually have no idea why deposition of ice in space should form amorphous ice rather than crystalline ice.
Sorry, I should have exapnaded. I meant thanks for advising that water can transfer form straight from gas to solid. That was the part I was trying to understand.
stan101 said:
Sorry, I should have exapnaded. I meant thanks for advising that water can transfer form straight from gas to solid. That was the part I was trying to understand.
what part of super cold do you not comprehend?
roughbarked said:
what part of super cold do you not comprehend?
the part that Moll explained.